Optical system and optical apparatus including the same

Abstract

An optical system in which a maximum value of a height from an optical axis of a paraxial marginal ray closer to an expanded side than a point of intersection between an optical axis and a paraxial chief ray, includes a lens unit Lr including at least one refractive optical element Gn of a negative refractive power. In the optical system, νd (Gn) as an Abbe number of a material of the refractive optical element Gn, θgF (Gn) as a partial dispersion ratio regarding g and F-lines, FGn as a focal lengths of the refractive optical element Gn, and Fr as focal lengths of the lens unit Lr are set appropriately.

1. An optical system in which a maximum value of a height from an optical axis of a paraxial marginal ray closer to an expanded side than a point P, P denoting a point of intersection between an optical axis and a paraxial chief ray, and in a lens surface of the expanded side is larger than a maximum value of a height from an optical axis closer to a reduced side than the point P in which the paraxial marginal ray passes through the lens surface,
 the optical system comprising: 
 closer to the reduced side than the point P, a lens unit Lr including at least one refractive optical element Gn of a negative refractive power in which light entrance and exit surfaces are both refractive surfaces made of solid-state material, 
 wherein when an Abbe number of a material of the refractive optical element Gn is νd (Gn), a partial dispersion ratio regarding g and F-lines is θgF (Gn), and a focal length of the refractive optical element Gn is FGn, a focal length of the lens unit Lr is Fr, the following conditions are satisfied:
   −2.100×10 −3   ·νd ( Gn )+0.693<θ gF ( Gn ) 
   0.55<θ gF ( Gn )<0.90 
   0.02<| FGn/Fr|< 10.00. 
 
 
   
   
     2. An optical system comprising:
 sequentially from an object side to an image side, a first lens unit of a positive refractive power and a second lens unit of a negative refractive power; 
 an aperture stop; and 
 closer to a reduced side than the aperture stop, a lens unit Lr including at least one refractive optical element Gn of a negative refractive power in which light entrance and exit surfaces are both refractive surfaces made of solid-state material, 
 wherein when an Abbe number of a material of the refractive optical element Gn, and a partial dispersion ratio regarding g and F-lines are respectively νd (Gn) and θgF (Gn), and focal lengths of the refractive optical element Gn and the lens unit Lr are respectively FGn and Fr, the following conditions are satisfied:
   −2.100×10 −3   ·νd ( Gn )+0.693< θgF ( Gn ) 
   0.55<θ gF ( Gn )<0.90 
   0.02<| FGn/Fr|< 10.00. 
 
 
   
   
     3. An optical system according to  claim 1 , wherein the Abbe number νd (Gn) satisfies the following condition:
   ν d ( Gn )<60. 
 
   
   
     4. An optical system according to  claim 1  wherein when a partial dispersion ratio of g and d-lines of the refractive optical element Gn is θgd (Gn), the following conditions are satisfied:
   −2.407×10 −3   ·νd ( Gn )+1.420<θ gd ( Gn ) 
   1.255<θ gd ( Gn )<1.670. 
 
   
   
     5. An optical system according to  claim 1 , wherein at least one surface among light entrance surfaces of the refractive optical element Gn is aspherical in shape. 
   
   
     6. An optical system according to  claim 1 , wherein at least one surface among light entrance surfaces of the refractive optical element Gn is in contact with air. 
   
   
     7. An optical system according to  claim 1 , further comprising, sequentially from the object side to the image side, a first lens unit of a positive refractive power which is immobile during focusing, and a second lens unit of a negative refractive power which moves in an optical axis direction for focusing. 
   
   
     8. An optical system according to  claim 1 , wherein when average Abbe numbers of materials of lenses of positive refractive powers and negative refractive powers in the lens unit Lr are respectively Vp and Vn, the following condition is satisfied:
   0.8< Vp/Vn< 1.8. 
 
   
   
     9. An optical system according to  claim 1 , further comprising, sequentially from the object side to the image side, a first lens unit of a positive refractive power which is immobile during focusing, and a second lens unit of a negative refractive power which moves in an optical axis direction for focusing,
 wherein when focal lengths of the first and second lens units and the entire system are respectively F 1 , F 2 , and F, the following conditions are satisfied:
   0.2< F 1/ F< 0.7 
   0.1<| F 2 /F|< 0.5. 
 
 
   
   
     10. An optical system according to  claim 1 , further comprising, sequentially from the object side to the image side, a first lens unit of a positive refractive power which is immobile during focusing, a second lens unit of a negative refractive power which moves in an optical axis direction for focusing, an aperture stop, a third lens unit of a positive refractive power which is immobile during focusing, a fourth lens unit of a negative refractive power which moves in a direction perpendicular to the optical axis to displace the image, and a fifth lens unit of a positive refractive power which is immobile during focusing,
 wherein the refractive optical element Gn is included in the fifth lens unit. 
 
   
   
     11. An optical system according to  claim 1 , further comprising, sequentially from the object side to the image side, a first lens unit of a positive refractive power which is immobile during focusing, a second lens unit of a negative refractive power which moves in an optical axis direction for focusing, an aperture stop, and a third lens of a positive refractive power which is immobile during focusing,
 wherein the refractive optical element Gn is included in the third lens unit. 
 
   
   
     12. An optical apparatus comprising:
 the optical system of  claim 1 .